In this update, we have added a new achievement called Pacifist Clear, which can be achieved by clearing the ZAKO RUSH without hitting any enemies with your ship's bullets or lasers and without making any mistakes.
The difficulty of some stages is incredibly low compared to normal play. You may want to try Pacifist Clear for stages that you have difficulty with in the main game play.

We have also updated the GBA version included as a bonus to a demo version that allows you to play all phases of Area 1 (1-1 to 1-4).
For more information on the GBA version, see the following article.
https://store.steampowered.com/news/app/3476490/view/547857372725379988
As a bonus, I also included the source code of the GBA version, which is written in high-level language (C) and is therefore easier to analyze than the Z80 assembly language source code of the original version (VGS-Zero).

In the next update, we plan to add the “PACIFIST CLEAR” achievement for clearing the ZAKO RUSH without a bullet or laser hit to the enemies.
We will also update the GBA version distributed as a freebie to a demo version in which all phases of Area 1 can be played, and will distribute the source code written in C for the GBA version along with it.
For more information on the GBA version, see the following article.
https://store.steampowered.com/news/app/3476490/view/547857372725379988